The proposed study focuses on understanding and developing new methods to diagnose low back pain problems resulting from both segmental instability and degenerative changes in intervertebral discs and/or facets. In the ongoing study, we found that a relationship exists between the severity of intervertebral disc degeneration and increases in torsional and flexion-extension movements. Significant differences were found in facet degeneration and disc degeneration between the asymptomatic and the symptomatic subjects. However, the mechanistic relationship between disc degeneration and the facet joint remains to be clarified. In Project 1 of the renewal Program Project Grant, we will define kinematic hypermobility in torsion and flexion-extension in vivo and correlate those measurements with low back pain symptoms. We will identify factors of prognostic importance to the progression of disc and facet joint degeneration and symptoms. We propose a five-year study of the in vivo relationship of degenerative changes with segmental instability of the lumbar spine. In this proposed study, we will re-evaluate, over a five-year interval, 25 asymptomatic normal subjects and 25 age- and sex-matched symptomatic subjects, who were investigated in the current grant cycle. Hypotheses that we will test in this study are (1) that greater segmental mobility and/or specific kinematic patterns contribute to accelerated intervertebral disc and facet degeneration over time, and (2) that load transmission through the facet joints depends on the loading direction and intervertebral disc degeneration and height, and motion segment level and facet orientation. The specific aims are (1) to measure changes in rotational and flexion/extension segmental movement associated with disc and facet degeneration over five years within each subject (a longitudinal in vivo study comparing normal subjects and mechanical low back pain subjects), and (2) to investigate, using cadaveric lumbar spines, relationships among disc degeneration and height, segmental movement, disc pressure and facet joint pressure, and to analyze correlations between altered kinematics and load transmission (an experimental in vitro study). The outcome from the proposed study is expected to be equally effective for diagnosis of cervical spinal instability and evaluating many of new motion preservation treatment alternatives in use or under development.